The present invention relates to a method for the preparation of an original, wherein the recording layer is information-wise and grid-wise exposed and developed to give a relief image. The recording layer is exposed information-wise through individual color separation originals which are transparent in the areas of the appropriate projection color in the particular color separation original and of which the part-image areas of the projection colors adjoin one another without overlap. In addition, an exposure, with grid patterns, separated in time from the part-image exposure, and an aqueous-alkaline development are performed.
Images which are grid-wise screened are produced by ZOD (Zero-Order-Diffraction) technique which is known from the journal, Laser u. Opto-Elektronik, No. 3/1976, pages 16/17. Three nickel matrices are produced from the relief images which, for example, correspond to three primary color grid patterns in yellow, magenta and cyan in a photo-lacquer, and these matrices are used to emboss colorless thermoplastic films of, for example, polyvinyl chloride. These films are mechanically superposed and, upon projection using conventional projectors, colored projection images are obtained from the colorless relief images. The grid-like screening is effected with relief grids of rectangular cross-section, the grid period being about 1.5 .mu.m. One nickel matrix of different relief depth is made for each color separation in magenta, yellow and cyan, and the separate embossed images are generated using these matrices. The relief depths differ, the relief depth of the cyan separation being the greatest and that of the yellow separation being the smallest. These color separation images are screened. The embossed images are superposed to give a three-layer relief image, from which colored images can be projected. The technique described gives very bright color images of high resolution. The relief images can be duplicated relatively cheaply and rapidly by embossing.
A disadvantage which makes the acceptance of this technique more difficult is the expensive preparation process with three completely separate working steps for making the individual embossed relief images corresponding to the color separations. A further disadvantage is the composing of the three separate relief images in a true fit to give the composite image required for the colored projection.
A solution which overcomes these disadvantages has already been suggested in co-pending patent application, Ser. No. 861,491, filed Dec. 16, 1977 by Roland Moraw et al and entitled "Information Carriers, Method of Forming and Copying Said Carriers". According to this teaching, the relief image is composed from the relief part-images corresponding to the individual color separations in such a way that areas of different color, which can also be screen dots in the case of screened images, are located in one plane, with these areas of different color not intersecting but at most touching one another. Relief images of this type are very suitable for depicting two-dimensional multi-colored originals, such as graphical illustrations, in the form of relief grid structures in one plane.
In the process disclosed in the aforementioned application, Ser. No. 861,491, the disclosure of which is incorporated by reference herein, the grid-wise exposure and the image-wise color separation exposures are carried out separated in time, the grid-wise exposure taking place right through the photo-lacquer or photo-resist layer down to the carrier material. This process utilizes three main colors.
A further development of the recording of the grid image uses four main colors, for which corresponding color separation originals are employed for the color separation exposures by simply contact exposure. This teaching is disclosed in Application Ser. No. 928,700, filed July 27, 1978 whose disclosure is hereby incorporated by reference herein.